A. Field of the Invention
This invention relates to wireless/cellular radiotelephone systems and more particularly to an apparatus and method for realizing a self-configurable allocation of radio frequency (RF) spectrum channels to the different cells within a cellular system.
B. Background Art
The service area of a wireless communications system is partitioned into connected service domains known as cells, where radio telephone users communicate, via radio links, with the base station serving the cell. The base station (BS) is coupled to the land network. Efficient use of the available radio frequency spectrum is achieved through the reuse of the same radio frequencies in designated co-user cells that are sufficiently separated by distance so that the combined interference generated by co-channel and neighbor-channel cells is below tolerable levels.
Historically, the assignment of radio frequencies (or channels) to cells has been based on regularity assumptions (i.e., equal-sized regularly-spaced cells with uniformly distributed traffic loads), which enable the adoption of simple rules for identifying co-user cells, and for partitioning the RF spectrum into channel sets. However, because such regularity assumptions often do not hold, and thus the rules of regular channel assignment do not lead necessarily to the efficient utilization of the RF spectrum, a channel assignment approach, known as non-regular channel assignment, has evolved for to address this deficiency. Both regular and non-regular channel assignment approaches can be classified as fixed channel assignment, which is characterized by a fixed relationship between cells and the channels serving them.
In contrast to fixed channel assignment methods, a new classification has been developed known as flexible channel assignment. Such flexible channel assignment methods, exploit the capability of a system for remote, software-driven, retuning of the base station radios, which capability enables channel capacity to adapt to traffic variation.
Wireless systems are generally migrating toward digital technologies from traditional analog wireless systems, although it is expected that analog systems will continue to serve a significant population of users for some time yet. In the digital environment, three candidates are emerging: Time-Division Multiple Access ("TDMA"), Global System for Mobile (GSM), and Code-Division Multiple Access ("CDMA"). The first two involve narrow-band channels that can carry, in separate time slots, three or eight conversations each, respectively. The latter uses wider channels that accommodate many users at once and can be re-used in abutting cells. From a service provider's perspective, one of the fundamental differences between the two technologies is the need for channel assignment in the former, a requirement that is absent in the latter. As will be apparent from the preceding discussion, channel assignment is very much a requirement for the analog systems used today.
The channel assignment function, as carried out in the prior art, is characterized by both the need for advanced planning of such channel assignments and a requirement for considerable data gathering. Additionally, such traditional channel assignment planning tends to achieve sub-optimal traffic loading in the cell of a wireless system, as well as sub-optimal traffic throughput in such a system.